>> reporter: steps away from their ultimate goal, the unthinkable. marathon runners and spectators violently injured. the two explosions going off within seconds of each other at boston's copley square. >> at first it sounded like a cannon blast. it felt so strong it almost blew my hat off. everybody started running the other way. there were people running over towards them to help the injured. there were really bad, bad injuries. some people were very, very badly hurt. >> reporter: the clock at the finish line read 4:09:43 when the first explosion went off on boylston street. the second a block away. a place of celebration instantly transformed into a scene of chaos. >> everything was normal. everyone was relaxed and happy. then the explosion right next to the finish line.

and then within another maybe 30 seconds, another explosion. and then pandemonium struck. >> reporter: now there was a race of a different kind -- to rescue people and save them. >> i was carrying somebody who lost both of their legs in the explosion. it was a lot of them with lost limbs. catastrophic. >> it was loud. it was really, really loud. then chaos everywhere. >> reporter: the smoke could be seen from across the charles river. boston police called in all off duty officers to help. ambulances took 19 victims to massachusetts general hospital. >> this is like a bomb explosion that we hear b about about on t in baghdad or israel or some other tragic place in the world. >> it was carnage. i saw a man who lost part of his leg. and all of the folks from the marathon were treating the runners and had to be called into action. >> reporter: 27,000 runners from 96 countries signed up for

the 26.2-mile race. those still on the course were diverted away from the finish line. authorities would not speculate on whether it was terrorism. >> we are not being definitive on this right now. you can reach your own conclusions based upon what happened. >> reporter: the race famous for heartbreak hill today the site of just heartbreak. tonight every police agency in the state of massachusetts is sending help to boston as is the federal government. bostonians are told to stay indoors. if they have to go out to avoid large crowds. while authorities try to figure out who brought to such a violent deadly end the day that people in boston, brian, have always called the very best day. >> absolutely. thank you very much for that. let's go to katy tur who made her way up there. as i understand it there are 15 blocks that are virtually frozen. people have been told to

shelter in place and once they go out, avoid crowds which is tricky on this day which is a holiday every year. >> reporter: it's pretty tricky in this area, brian. this is the back bay of boston. it is a popular area. it is a busy area on a normal day. it is chaotic here during the marathon in a good way. it's celebratory. the bars are open. people are out. right now there are people here. they want to see what's going on. i guess they are trying not to congregate. for the most part it's quiet for this area. after the explosion there were streams of people walking the streets. the subways were shut down and because of that, people had to walk for miles in some cases to their destination. in fact, we are two blocks from the finish line. two blocks from where the explosions happened. we saw a woman right over here, witnesses saw her stumbling to this block with shrapnel wounds. nbc has confirmed shrapnel was part of theegs -- these explosions.

that's why there were lower limb injuries. people reported seeing tourniquets applied on the raceway. back bay is normally a busy area. the streets are closed right now. there are a number of roadblocks throughout the area. there was a ground stop at logan airport. we had to circle over providence for quite a while before they allowed us to land. as you would imagine, a very heavy police presence here. the national guard is here and people are on alert. they want to know what's going on. the police commissioner asked everybody to stay inside, everybody to go home if they can. from what you can tell although there are people out here, most of them have heeded that order, at least around here. brian? >> we can see looking at tape of the finish line the digital seems to say this was the 4:09, four hour, nine minute finishing mark. if you are crossing the finish line at that point in this race you have done very well. to finish at all you have done very well. but people thought, and you can't blame them, that this was some kind of cannon, a planned

thing. i had one eyewitness describe it in terms of world trade. that once the second building was hit that day we knew it was something different. well once the secondary explosion went off, they knew it was not an accident of the construction of the city like a gas main. >> reporter: certainly when you're at a marathon, especially in boston where they haven't had issues like they have had in new york, nobody was expecting something like this to happen. initially nobody thought -- they weren't sure if it was even an accident, a gas main break. people didn't know what was going on. when the second explosion happened 15 seconds later people started to believe there was something fishy, something bad. that's when people started to get scared, run away. a bit of a chaotic scene out here. brian? >> katy tur on the streets of boston tonight. for a 15-block area people

aren't allowed. we don't know when people will be allowed back in. to washington we go. our justice correspondent pete williams has been working this story all day. pete, what can you tell us tonight? >> tonight authorities confirm that there were two bombs. we know that much. but it's unclear how many others were planted. they say there were other suspicious packages. and the word, of course, of another bomb elsewhere placed at the jfk library is apparently turning out not to be true. at least five other packages have been found on the street, have been deemed suspicious and are being destroyed. but there is no firm confirmation of whether they were actually explosive devices although some officials tonight say there is reason to think that some of them were. we are told, by the way, that one of the two victims killed in the explosion was 8 years old. boston police say there was no specific intelligence warning of any kind of attack. federal officials tonight say there is no reason to think that this is part of any larger threat. at this point they believe it is confined to boston. but a meeting tonight will

decide whether any kind of national alert will be sent out. there is no suspect in custody, authorities say. but some people are being questioned including some with injuries who were taken to boston hospitals. one of those, a person in whom there is some interest is a young person who was here on a student visa. brian? >> pete williams in our washington newsroom. we'll look for further details from there. pete, thanks. michael leiter is our national security analyst at nbc news, former director of the national counterterrorism center in washington. michael, two things. overseas veterans of the wars the past ten years and those of us who spent time there, number one, the primary explosion, then the secondary explosion as people are running to the first. and number two, the nature of these injuries. an explosive device apparently with added shrapnel.

that haunts everybody involved. >> yes, brian. the idea of using two explosive devices, the first charge which attracts to some extent the first responders -- police, fire, medical -- and then have a second charge go off that's targeting those responders potentially is the sign of a more sophisticated attack. as you noted, the shrapnel, the idea there could have been ball bearings or something else in these explosives specifically trying to kill or maim, not just trying to have a small explosion and get some attraction. the sign of a terrorist organization that's trying to kill people. >> here we are in the post 9/11 era. while it's familiar now to us in a kind of hideous way, it also isn't. we should emphasize that while people, especially in big cities and especially on the east coast, are going to see precautions at train stations and airports and perhaps big obvious movement of law enforcement, there is no reason

to fear that this is any, at this hour, part of any wider plan. correct? >> that's right. people should view the precautions in washington, new york, san francisco, los angeles merely as precautions. this is exactly what the federal government and states and cities prepare for in the event of an attack. heightening basic preparedness, putting more police on the scene. that is not because they know something specific. it is because everyone wants to make sure that there is a show of force and should something else arise that they are in a good position to respond. but it is not the sign of a specific threat necessarily. >> michael leiter in our washington bureau. michael, thank you as always. across town we go to the white house. chuck todd was standing in the briefing room when the president entered at about 6:10 tonight to give his remarks on what the white house was saying so far. chuck? >> i can tell you this.

one of the things the president did not say is he did not call this terrorism. i can tell you from talking to sources this was discussed and the decision was made not to have the president use that specific word. a national security official e-mails and says this. any event with multiple explosive devices as this appears to be is clearly an act of terror and will be approached as an act of terror. however we do not know who carried out this attack. a thorough investigation will determine whether it was planned and carried out by a terrorist group, foreign or domestic. they are careful with their language. we know the president has been briefed all day from the fbi director, homeland security director, chief terrorism adviser. he himself has been giving briefings to the leadership in congress. but i can tell you in talking to officials around here, brian, there is a little bit of frustration of how little they do know at this point in time which is why the president was clearly being very careful with the language he chose to use. >> chuck todd at the white house, thanks. we'll take a quick break. when we come back, we'll talk

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stop taking viagra and call your doctor right away if you experience a sudden decrease or loss in vision or hearing. this is the age of taking action. viagra. talk to your doctor. we are back tonight. this is the scene as it happened. 2:50 p.m. this afternoon in boston during the marathon. there is the explosion. one runner hit by shrapnel goes down. this is an important point here. between the point of the explosion and the crowd police, boston ems, race volunteers were caught up in it. they were among the targets. so having seen this, having witnessed this, the question becomes how can we ever keep our public events safe if someone was allowed to get two devices this close to this classic a day in boston, massachusetts? nbc's tom costello has been looking at this conundrum for

security personnel all day. tom, evening. >> reporter: hi, brian. we talk about how security changed after 9/11. and it did. but security experts have been dealing with terrorist threats at big gatherings since the munich games in 1972. trying to ensure everyone's safety is a herculean challenge. for any police agency planning for big crowds means months of nightmares. secures and stealing a course like the boston marathon with 20,000 runners and half a million spectators is almost an impossible challenge. bill bratton was the boston police commissioner before leading the nypd and the lapd. >> it is extraordinarily difficult, as you might imagine, that 26-mile route. double it, 52 the miles because you have two sides of the street. most of the security would be focused on the finish line area where the actual bombing occurred. >> reporter: atlanta, 1996. a backpack holding pipe bombs

packed with nails exploded in olympic park. two died. more than a hundred wounded. it wasn't until 2003 that police tracked down domestic terrorist eric robert rudolph. >> get back, please! >> reporter: london, 2005. a series of coordinated suicide attacks on the subway and bus system left 52 people dead, 700 injured. the attackers used home made explosives packed into backpacks. those attacks on finds of the secret service when president obama was sworn in for the first time in 2009. dan bonngeno was the lead secret service agent as people packed the national mall in downtown d.c. a potential terrorist could have been hiding in plain sight. >> you can't guarantee anything. you reduce the probability to hopefully something minuscule so if something happens your response is enough to keep casualties to a minimum n times square 2010. a car bomb failed to explode and was disarmed before it could

hurt anyone. two days later a pakistani-american was caught trying to board a flight to the middle east. big sporting events like the boston marathon had been viewed as inviting targets since 9/11. the marine corps marathon attracts 30,000 runners each year. super bowl organize ohhers are often criticized for too much security at the big game. and securing every possible public event that could invite an attack is respond reasonable. michaelle leiter was the counter terrorism director under president george w. bush. >> you can't protect all of the people at all of the large sporting events or any public gathering. that's the advantage terrorists have. they can look for the softest, least defended area. >> it is not unusual to see trash bins removed, mailboxes removed, even the manhole covers screwed down. that's the kind of extraordinary security you get in a presidential zone. putting in place that kind of security at an outdoor marathon,

brian, would be a different matter. >> again, how ironic this happened at what was perhaps the most secure zone in all of boston along those 26 miles today. tom costello from washington tonight. tom, thanks. we'll take another break. when we come back, an eyewitness to today's bombing. [ male announcer ] this is kevin. to prove to you that aleve is the better choice for him, he's agreed to give it up. that's today? [ male announcer ] we'll be with him all day as he goes back to taking tylenol. i was okay, but after lunch my knee started to hurt again. and now i've got to take more pills. ♪ yup. another pill stop. can i get my aleve back yet? ♪ for my pain, i want my aleve. ♪ [ male announcer ] look for the easy-open red arthritis cap. from capital one... boris earns unlimited rewards for his small business.

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and i felt it go through think leg into my chest. i was sitting down. e everyone in the room, everyone outside just stops moving and instantly had no idea what was happening until that second bomb went off. that second bomb you felt just as much, you heard just as loud and everyone instantly knew that it was not what we thought and it was a bomb. at that very moment i walked outside. i looked down the street and you could see smoke coming. people's faces instantly changed from smiles to tears and fear and were basically running for their lives. you could look at any direction at any moment at the intersection and there were thousands and thousands of people that you could see in any direction shutting down the streets. >> if there was a blessing it was that the medical tent was right there at the conclusion of the race. you had medical professionals and a lot of boston p.d. already

on the scene. >> yeah. i'm staying at the fairmont and the medical tent is outside our front door. it was one of the craziest scenes i have seen. everybody was rushing. no one knew what to do. ems was running toward the scene. everyone was in fear. >> also the definition of terrorism. it's the last thing you expect at the finish line of the boston marathon on patriots day in boston. serdar ozturk, thank you very much. another break and we are back with more after this. the battle of bataan, 1942. [ all ] fort benning, georgia, in 1999. [ male announcer ] usaa auto insurance is often handed down from generation to generation because it offers a superior level of protection and because usaa's commitment to serve the military, veterans, and their families

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[ static warbles ] [ beeping ] red or blue? ♪ marathon day, patriots day is supposed to be a great day every day in boston. instead this year it turned into a horrible day. nbc's katy tur is on the streets of boston tonight. what can you tell us there? >> reporter: brian, the sun is setting here and the runnerers are making their way back home, back to your hotels. families are reuniting with loved ones, trying to see if everyone is safe. being glad so many are safe tonight and trying to get their head around just what happened in all of the tragedy that

unfolded. again, we are in the back bay of boston. h this is a very popular area. after the marathon right about now this area would be crowded. it is right now pretty dead. it is very far from normal, brian. it will be very far from normal for quite some time. >> katy, thanks. that's going to conclude our regular half hour of nbc "nightly news" for tonight. if your station is carrying it, we will be right back on the air with a special hour-long edition, a second half hour of the broadcast. if not, it will be available on our website. and an early heads-up, we are back on the air tonight at 10:00 p.m. eastern, 7:00 on the west coast with a primetime special on what's happened in boston today. -- captions by vitac -- www.vitac.com >> announcer: terror in boston. this is nbc "nightly news" with brian williams.

>> announcer: terror in boston. this is nbc "nightly news" with captions paid for by nbc-universal television that is what it looked like at ground level. the finish line at the boston marathon. it was after the first, the top tier of finishers. it was at the four ur, nine minute mark, exactly 2:50 this afternoon when first one

explosion and then a secondary explosion went off. people couldn't imagine what the first one was, but with the second they knew, they suspected it was some sort of attack. it appears tonight we are coming on the air yet again in this post 9/11 era with word of an apparent terrorist attack within our shores. a terrible day in boston on what is a holiday in that city. it is patriots day. they mark the lexington and concord battles. the red sox play baseball and they run the boston marathon. tonight the death toll stands at two. over 100 injured. we want to go to jonathan hall who reports from whgh tv. we have been watching their live coverage and airing it to a national audience. jonathan, you are at brig ham women's hospital where they took

some of the injured, correct? >> reporter: that's right. boston-area hospitals have been completely inundated with patients. they drill for this. they say they are up to the task and they are ready, treating seriously injured people. this knows no bounds. it didn't discriminate on age or gender. we understand here patients ranged in age from 3 to 62, both men and women. dozens pea being treated here. we saw fbi agents, atf agents going in and out. massachusetts state police, the boston s.w.a.t. team is guarding the entrance of the hospital. it is on lock down. nobody in, nobody out unless they have the proper identification. of course, relatives of those injured are allowed access to the hospital. once again, a lot of people here coming in, coming out. we have seen people crying. we have heard the stories as